| Abstract | Styrene and benzene are petrochemicals which have been used extensively in the manufacture of plastics and fibers. These chemicals are genotoxic compounds and probably related to cancer in human. This study aims to assess occupational exposure to styrene and benzene through the use of biomarkers. In this study, assessment of occupational exposure to styrene and benzene was conducted in 35 workers from styrene-reinforced fiberglass factory and 31 controls from non-exposed work unit. Exposure to styrene and benzene was studied by analysis of these compounds in workplace and in individuals. Various biomarkers of exposure were employed including measurement of blood concentration of styrene and benzene using GC/MS as well as analysis of urinary metabolites by LC/MS-MS; hippuric acid (HA), mandelic acid (MA), phenylglyoxylic acid (PGA) for styrene exposure and trans,trans-muconic acid (t,t-MA) and S-phenylmercapturic acid (S-PMA) for benzene exposure. The median level of styrene and benzene in the fiberglass factory were 3.55 ppm and 5.43 ppb, respectively. Whereas, styrene was non-detectable and median level of benzene concentration was 5.18 ppb in the control workplace. Median level of individual exposure to styrene was 5.66 ppm in factory workers; however, styrene was not detected in all control subjects. Blood styrene level was significantly increased in exposed subjects (p<0.001) compared to control. Post-shift levels of urinary metabolites of styrene in exposed subjects were significant higher than those of control. The increased levels of HA, MA, and PGA were approximately 4-fold (p<0.001), 30-fold (p<0.001) and 300-fold (p<0.001), respectively. Level of HA, MA and PGA at post-shift was significant higher than pre-shift in exposed subjects, but not in control. Among factory workers, styrene exposure was highest in the resin laminating workers (22.71 ppm) compared to trimming (3.73 ppm) and painting workers (4.59 ppm). This was in accordance with a significant increase in blood styrene concentration and urinary metabolites of styrene in the resin laminating workers, compared to the other two groups of workers. Benzene exposure was significant increase in factory workers (18.26 ppb; p<0.001) compared to control (6.49 ppb). Blood benzene level and post-shift level of t,t-MA and S-PMA were significantly increase in exposed workers. Factory workers stratified by job activity showed that there were no significant difference of exposure level among study groups, but blood benzene level in resin laminating workers was significant lower than that of trimming and painting workers. However, post-shift level of t,t-MA and S-PMA expressed as ml urine basis were not significant difference among groups. In conclusion, fiberglass factory workers in this study exposed to styrene and benzene at a significant higher level compared to control. Level of all study biomarkers were significantly increased in exposed subjects. Blood styrene provided strong correlation with level of exposure. Based on increased level from control of the study metabolites of styrene, PGA was the most sensitive biomarker of exposure to styrene compared to HA and MA. On the other hand, significant relationship between benzene exposure and level of benzene metabolites, t,t-MA and S-PMA, were not found. According to ACGIH, median exposure level of styrene or benzene in exposed subjects was not exceed the TLV-TWA values, however health risk of simultaneous exposure to these genotoxic compounds is necessary to study. |